Tina wrote in news:d86791d1-d1cd-4256-8c9e-
:

On Jun 3, 11:35 pm, Bertie the Bunyip wrote:
Tina wrote in news:28472a75-654d-447f-9317-
:





On Jun 3, 10:25 pm, Bertie the Bunyip wrote:
Tina wrote in news:d9fb071f-4d30-45c3-
916d-
:

I understand how positive dihedral helps dynamic stability in
airplanes, but some big ones, like the Russian An 124 Condor,
has a
pronounced negative dihedral -- the wings have a noticeable
downward
slope.

That's called Anhedral..

Q1: Do those airplanes need active fly by wire controls to
maintain
stability, or is something else at play that keeps them right
side
up?

Nope.

Q2: Does anyone have a design rationalization for such a
configuration, as opposed to just zero dihedral? I can
appreciate
why
fighters have it -- they exploit lack of aerodynamic stability
for
rapid maneuvers -- but transports that spend their whole life
being
straight and level are another issue.

Well, the anhedral negates what can be excessive stability that
comes
form the sweep of the wings. Sweep provides a very similar kind of
stability as does dihedral and the addition of anhedral negates
some
of
this and keeps the airplane form becoming so stable that it can't
even
be maneuvered!
Most of the airplanes with pronounced anhedral are high wing and
would
have parasol stability as well. The anhedral helps neutralise some
of
that. Some low wing Russian jets have anhedral, but it's quite
small
Their sweep is quite marked and the anhedral is there to
ammeliarate
that. The 727 had a fairly radical sweep and you will notice, that
though it has dihedral it's very little compared to the 737 or
similar.

Note: I have not morphed into an Mx clone!

We'll know for sure if you tell me this answer is completely wrong
because your MSFS 172 doesn't have anhedral.

Bertie

Only after a very hard landing would a 172 develop negative
dihedral.
A Mooney, on the other hand, given the placement of the wheels,
would
either increase its positive dihedral, or more likely, given how
strongly they are built, put a dent in the runway.

I think there have been a couple of straight wing airplanes wiht
anhedral, but I can't picture one off the top of my head. Surely
everything that can be tried, has been tried at this stage!

Bertie

The everything that can be tried had been tried notion is out of
fashion, I don't think the patent office will be closing anytime soon,
or that Ratan's Scaled Composites will be closing up his shop. You can
bet someone will be trying an airplane with one wing over the other
soon. What would you call such a thing -- a redundant winged airplane?
For sure, in these days of political correctness, it would not be
called bi, would it?

Well, years ago a hypersonic bipe was looked at, believe it or not, but
even Beurt Rutan will tell you that none of his creations were
completely original. Not to detract from his talent, whihc is monstrous,
but there's nothing on any of his airplanes that hadn't been done
before. Even that mad boomerang has precedants and quite a lot of them
dating back to the first world war (Caproni). Getting it all arranged
right to make it go better than anything before it is his gift. Having
said that, Spaceship one was pretty unique, but you'll probably find
that mad recovery system was done in boost glider in an old issue of
American Aircraft Modeler or similar. I never cease to be astounded at
the massive number of airplanes constructed in th elast century and the
variety. it hardly seems possible sometimes that there were enough
people to make them all!


Bertie



Bertie

Where are my meds?